MAX1401EAI+ Maxim Integrated Products, MAX1401EAI+ Datasheet - Page 34

• Manufacturer Part Number: MAX1401EAI+
• Description: IC ADC 18BIT LP 28-SSOP
• Manufacturer: Maxim Integrated Products

Specifications of MAX1401EAI+

• Number Of Bits: 18
• Sampling Rate (per Second): 480
• Data Interface: QSPI™, Serial, SPI™
• Number Of Converters: 1
• Power Dissipation (max): 750µW
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-SSOP
• Number Of Adc Inputs: 5
• Architecture: Delta-Sigma
• Conversion Rate: 4.8 KSPs
• Resolution: 18 bit
• Input Type: Voltage
• Interface Type: Serial
• Voltage Reference: External
• Supply Voltage (max): 3 V
• Maximum Power Dissipation: 21.45 mW
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Input Signal Type: Pseudo-Differential, Differential
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

+3V, 18-Bit, Low-Power, Multichannel,
Oversampling (Sigma-Delta) ADC
Figure 15. Thermocouple Application with MAX1401
Figure 16. 4–20mA Transmitter
34
THERMOCOUPLE
JUNCTION
______________________________________________________________________________________
+3V
SENSOR
+1.25V
R
R
C
GND
V+
SPI
4
C
ISOLATION
BARRIER
AIN1
AIN2
REFIN+
REFIN-
AGND
SWITCHING
NETWORK
SPI
4
MAX1401
µP/µC
DGND
BUFFER
SPI
3
GND
DAC
V+
PGA
R
GAIN
Low power, single-supply operation, and easy interfac-
ing with optocouplers make the MAX1401 ideal for
loop-powered 4–20mA transmitters. Loop-powered
transmitters draw their power from the 4–20mA loop,
limiting the transmitter circuitry to a current budget of
4mA. Tolerances in the loop further limit this current
budget to 3.5mA. Since the MAX1401 consumes only
250µA, a total of 3.25mA remains to power the remain-
ing transmitter circuitry. Figure 16 shows a block dia-
gram for a loop-powered 4–20mA transmitter.
No specific power sequence is required for the
MAX1401; either the V+ or the V
up first. While the latchup performance of the MAX1401
is good, to avoid latchup it is important that power be
applied to the MAX1401 before the analog input signals
(AIN_) or the CLKIN inputs. If this is not possible, then
the current flow into any of these pins should be limited
to 50mA. If separate supplies are used for the
MAX1401 and the system digital circuitry, then the
MAX1401 should be powered up first.
R
R
OFST
FDBK
C
C
Loop-Powered, 4–20mA Transmitters
REGULATOR
VOLTAGE
R
Y
R
R
X
SENSE
DD
4–20mA LOOP
Power Supplies
INTERFACE
supply can come
V
V
IN+
IN-